Micro-fluid ejecting devices such as ink jet printers continue to be improved as the technology for making the printheads continues to advance. New techniques are constantly being developed to provide low cost, highly reliable printers which approach the speed and quality of laser printers.
One area of improvement in the micro-fluid ejecting devices is in the ejection head itself. This seemingly simple device is a microscopic marvel containing electrical circuits, fluid passageways and a variety of tiny parts assembled with precision to provide a powerful, yet versatile component of the printer. The components of the ejection head must also cooperate with an endless variety of fluids to provide the desired ejection functions. Accordingly, it is important to match the ejection head components to the fluid and the duty cycle demanded by the ejection application. Slight variations in production quality can have a tremendous influence on the product yield and resulting ejection head performance.
A micro-fluid ejection head typically includes a semiconductor chip and a nozzle plate attached to the chip. Flow features, including fluid flow channels and fluid ejection chambers are included in the nozzle plate or in a separate thick film layer attached to the semiconductor chip between the nozzle plate and the chip. The semiconductor chip is typically made of silicon and contains various passivation layers, conductive metal layers, resistive layers, insulative layers and protective layers deposited on a device surface thereof. Individual fluid ejection actuators such as heater resistors are defined in the resistive layers and each fluid ejection actuator corresponds to a nozzle hole in the nozzle plate for ejecting fluid from the micro-fluid ejection head. Fluid is supplied to the fluid flow channels and fluid ejection chambers from a slot which is formed as by chemically etching, grit blasting, or a deep reactive ion etching (DRIE) technique such as is described in U.S. Pat. No. 6,402,301 to Powers et al. through the thickness of the semiconductor chip.
As advances are made in fluid ejection speed and accuracy, a need arises for an increased number of ink ejection actuators which are more closely spaced on the silicon chips. Decreased spacing between the ink ejection actuators requires more reliable fluid feed techniques for supply fluid to the individual fluid ejection actuators. As the complexity of the micro-fluid ejection head continues to increase, there is also a need for long-life ejection heads that can be produced in high yield while meeting more demanding manufacturing tolerances. Thus, there continues to be a need for improved manufacturing processes and techniques which provide improved ejection heads and ejection head components.
With regard to the above and other objects, the disclosure provides methods for improving fluid flow in one or more flow features of a micro-fluid ejection head. One such method involves bonding a substrate having a flow feature layer to an ejection head body using a relatively low stress, substantially flexible adhesive containing a relatively volatile polar organic compound. The adhesive is cured under conditions sufficient to induce outgassing of at least a portion of the relatively volatile polar organic compound on at least a portion of a flow feature surface sufficient to increase fluid wetting of the flow feature surface.
In another exemplary embodiment, the disclosure provides a micro-fluid ejection head having a substrate holder, a substrate, a relatively low stress, substantially flexible adhesive adhesively attaching the substrate to the substrate holder on a first surface of the substrate, and a flow feature containing material adjacent a second surface of the substrate. The adhesive is effective to increase the surface energy of one or more of flow features in the flow feature containing material.
Yet another embodiment of the disclosure provides a method for increasing the surface energy of one or more flow features of a micro-fluid ejection head. A substrate is adhesively bonded to a substrate holder using a relatively low stress, substantially flexible adhesive containing from about 1 to about 50 percent by weight of a relatively volatile polar organic compound. The adhesive is cured under conditions sufficient to promote deposits of the polar organic compound on one or more surfaces of the one or more flow features thereby increasing the surface energy of the one or more flow features.
An advantage of at least some of the exemplary embodiments described herein is that fluid flow through narrow channels or passages in a micro-fluid ejecting head can be significantly improved. Without desiring to be bound by theory, it is believed that the relatively volatile polar organic compound may mask hydrophobic compounds and monomers that also deposit on the flow feature surfaces during the curing process. The hydrophobic compounds and monomers lower the surface energy of the flow feature surfaces while the relatively volatile polar organic compounds increase the surface energy of the flow feature surfaces.
Surfaces with relatively low surface energy have decreased wettability as compared to surfaces having relatively higher surface energy. As the wettability of the flow feature surfaces decreases, the resistance to fluid flow through the flow features is increased. Increased fluid flow resistance may contribute to reduced fluid flow or fluid starvation to ejection chambers of the micro-fluid ejecting head. Under high frequency operation, misfiring of the ejection actuators may result if the ejection chambers are not adequately refilled between fluid ejection actuation cycles. By increasing the surface energy of the flow features, the disclosed embodiments may significantly improve fluid flow to the ejection chambers.
Additionally, flow features having relatively low surface energy are more likely to attract and hold air bubbles which can impede fluid flow. While not desiring to be bound by theory, it is believed that increasing the surface energy of the flow features reduces the accumulation of air bubbles in the flow features of the micro-fluid ejection head.